The ABS slippery dip

The ABS slippery dip

23 August 2004Peter McKay

Last week's downpour is a timely reminder about the value of anti-lock brakes when trying to stop in an emergency in slippery situations. But do drivers know how to use the technology properly? Crash figures suggest not.

Despite its clear technical advantage over regular brakes, safety experts are puzzled why crash rates for cars equipped with anti-lock brakes are the same as those without.

The experts believe the problem is a lack of education. Stephan Presser recalls that in 1983, when he was being taught to drive in his home country of Germany, along with city and rural driving and after-dark supervision at highway speeds, his driving school instructor also showed him how to do emergency stops with a car equipped with ABS.

"As a teenager, I learnt very quickly that you could steer while braking very hard," says Presser, who is now a vehicle dynamics engineer at Ford Australia.

As with many safety experts, Presser is puzzled about reports, particularly those from the United States, suggesting that ABS-equipped vehicles are involved in as many crashes as vehicles not equipped with the system. Yet, unquestionably, with a smart driver at the wheel, cars with ABS generally stop faster than cars without. Test track results show conclusively that ABS cuts stopping distances on every surface, except gravel and some corrugated or bumpy roads, while also allowing the driver to steer around dangerous situations.

Presser says he has done exhaustive tests at speeds between 50 and 100kmh, on wet and dry tarmac and ABS consistently stops a vehicle in shorter distances. And ABS prevents wheels from locking up, which can cause a vehicle to skid out of control. It also allows the informed driver to steer around a potential hazard, even with the brake pedal firmly pressed.

So why isn't it working in the real world? Maybe because ABS will not stop a vehicle sliding off the road if it enters a corner too fast. Nor will it prevent you from crashing into the car in front of you if you haven't left enough space.

Many car company engineers are disappointed that Australians are paying for ABS on their cars but in most cases drivers are not aware of how to use the life-saving technology to avoid crashes.

The manager of Mitsubishi Australia's Special Projects Centre, Rob Chadwick, is adamant that, when used properly, ABS is an excellent tool to avoid a crash, or minimise the impact speed.

He suggests it gets a bum rap in some quarters because few drivers of ABS-equipped vehicles have either experienced it, or been taught how the system feels and reacts. "Because they start learning the practical side to ABS at the same instant that they are trying to avoid crashing, while they are in maximum panic mode, the outcome is not often pretty," Chadwick says. "I strongly advocate drivers of ABS vehicles being given the opportunity to experience an ABS stop and manoeuvre before they encounter a need to use it." Chadwick believes that with correct training of drivers, crash data would swing in the right direction.

The characteristics of ABS are rarely pointed out to motorists when they take delivery of a new car. Nor are they advised of the pulsating sensation through the brake pedal that means the anti-lock system is working. Presser adds that some drivers simply expect too much from ABS.

Then there are some deluded drivers of non-ABS cars who boast they can beat the stopping and steering abilities of ABS. Presser thinks differently, pointing out that no human can better a system that, in the case of the new Territory, can pulse at 100 times a second, keeping the braking performance constantly in the sweet spot.

As well, ABS also instantly and constantly regulates the pressure on all four wheels independently; a driver of a non-ABS car has just one brake pedal serving all four wheels.

Crucially, ABS requires an understanding by the driver of how to best optimise its benefits. If a driver is hesitant or doesn't apply full pressure on the brake pedal, ABS may not even be triggered.

New technology can improve ABS effectiveness. Now being offered on many new vehicles, Brake Assist senses when a driver wants to make an emergency stop and reduces the pedal effort required to make an ABS stop.

On the positive side, ABS is also far superior on split surfaces. For example, when the left-side wheels are on the dirt verge and the right-side on the bitumen. In a non-ABS car, this has the potential to send the vehicle towards the middle of the road. An ABS-equipped car would stop in a straight line. ABS also prevents rear-wheel lock-ups which may send the vehicle into a spin.

The gravel-road performance of ABS has long been an area of criticism. Here, a non-ABS car can stop better if the driver locks the wheels and in so doing cuts beneath the loose surface to build a wedge of dirt in front of the tyres.

Mitsubishi's Chadwick says crash data looks bad because many drivers believe having ABS makes them invincible even though they have never used the system in an emergency.

Chadwick says it is also important to understand that not all ABS systems are created equal. Today's ABS technology is significantly better than that fitted to cars 10 years ago. And European systems tend to have excellent snow/ice calibration but fall down badly when surfaces change and on dirt.

Meanwhile, the Department of Transport and Regional Services says it is unaware of any research results that would confirm the benefits (or otherwise) of ABS. "It is notoriously difficult to try to determine the effect of individual technologies on accident statistics given the range of variables involved," says its assistant secretary of vehicle safety standards, Peter Robertson.

"The presence of ABS obviously puts optimum braking performance within reach of the average driver but just how often it is called upon is not clear," Robertson says. "It would be a hard proposition to assert that the average motorist would be better off without it."